6
3.2. Discharging
(low voltage urgent and non-urgent alarm)
As a rule, installations will be equipped with a regulator whose voltage
threshold values will protect against deep discharge:
Discharge time
10h
120h
240h
Low voltage alarm
1.92V
1.92V
1.95V
Disconnect voltage
1.80V
1.85V
1.90V
3.3. Setting Charging Voltages
(solar charge on and solar charge off voltages)
In order to ensure optimum recharge, the following setting charge
disconnect and restart voltages can be applied:
Temperature
-20 to
0ºC
0 to
20ºC
20 to
35ºC
> 35ºC
Low recharge-restart
voltage (Vpc)
2.35V
2.30V
2.30V
2.25V
High recharge-dis-
connect voltage (Vpc)
2.50V
2.45V
2.40V
2.35V
For a battery discharged to 80% of its rated capacity within 120
hours, in optimum sunshine it will take around fifteen days to
recharge the cells and a further fifteen days to equalize their specific
gravity.
4. Service Life
Under normal operating conditions, the battery lifetime largely
depends on the temperature and depths of discharge. The service
life in cycling applications based on the number of years with a daily
DOD can never exceed the design life at 20°C of 20 years.
Influence of temperature
Example of an Powersafe TS battery cycling with 25% daily:
Average
temperature
of cells
Number of
cycles
at 25°C
Compensation
coefficient
Estimated
average
number of
cycles
at average
temperature
25ºC
5200
1
5200
30ºC
5200
0.83
4316
35ºC
5200
0.71
3692
Influence of depth of discharge
See curve (section 3.1), relative to number of cycles according to
DOD at 25°C.
Example of an Powersafe TS battery at 25°C:
Daily depth
of discharge
Number of cycles
at 25°C
Estimated service
life at 25°C
25
5200
> 14
5. Maintenance, Checks & Data Recording
5.1. Water Consumption
Flooded batteries require maintenance watering.
Water consumption depends on the charging current at a given
temperature.
Example for a battery fully charged with a constant voltage
of 2.35Vpc
:
Temperature
25°C
35°C
45°C
Charging current
mA/Ah
1
4
9
Water consumption
ml/Ah/year
2
10
25
Because there is a large electrolyte reserve, water may be added
just once a year.
Exact watering frequency will be determined by climate conditions
and the battery location.
Top up the electrolyte level (only with demineralised water) to the
nominal level, without exceeding the “max” mark.
5.2. Checks & Data Recording
• The containers and lids should be kept dry and free from dust.
Cleaning must be undertaken with a damped cotton cloth without
additives and without manmade fibres or addition of cleaning
agents, never use abrasives or solvents. Avoid electrostatic
charging.
• Every 6 months, check total voltage at battery terminals, cell
voltages & electrolyte specific gravity (electrolyte level &
temperature) of pilot cells, the cells surface temperature and
battery room temperature.
• Once a year, take readings of individual cell voltages too.
• Keep a logbook in which the measured values can be noted as
well as time and date of each event like commissioning date,
water consumption, discharge tests, topping-up dates etc.
